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Thursday, February 03, 2011

You can't always infer A from B.

Apparently the Songbird Survival Trust have asked the Game and Wildlife Conservation Trust to carry out a cull of magpies and crows. Their logic?

For example, the crow population has increased 200 per cent in the past 50 years but some smaller species have declined.

It’s about getting balance. Our job is to do this work and make recommendations because our science is well respected.

It’s a small-scale experimental study designed to improve the breeding success of small farmland birds, like buntings and yellow hammers,

Now I hate to disillusion them but because Crows have increased you can't infer that that is why smaller birds have declined. I think you'll find that nature normally allows compensates for such imbalances. It has probably got much to do with pesticides and lack of hedgerows etc. As a number of farmers in Norfolk have shown if you provide the habitat then the birds will come back.

edited for accuracy - thanks to the Wessex Reiver.


holdingmoments said...

I was appalled when I read about this the other day Pete. They were saying Crows and Magpies were responsible for farmland bird losses.
I suppose nothing to do with the things you mentioned, or habitat loss; building on what was once farmland.
Cormorants were also on a hit list, because they eat fish that are supposed to be for fishermen.
The worlds going mad.

Tricia said...

Do they expect their reasons to be believed? !!

The Wessex Reiver said...

Hi Pete, it is actually a small organisation called the Songbird Survival Trust who have asked the Game Conservancy to do this. I agree with you, get the habitat right, the rest look after themselves. Corvids do take songbirds, but are not responsible for the catastrophic decline in passerines especially on farmland, there are a whole raft of factors, disease, farmland practices, rapid expansions (and now declines) in the 1970's.

The Game Conservancy are a shooting organisation but since the 1960's have run a lot of valuable research into game birds and farmland species in particular, and are heavily involved with the Mammal Society, BTO etc. A lot of evidence say on hare numbers increasing comes from their Game Bag Census. At the moment thay are running a very interesting woodcock research programme to establish where woodcock migrate to and from.

Always difficult as I don't like to think of anything being shot, but it happens, and if us conservationists can get some valuable research out of their work, that has to be a good thing. I do worry though about orgnisations like the Songbird Survival Trust who are happy to have other birds killed for their own aims. Quite odd that.

ShySongbird said...

I too heard about this a couple of days ago Pete and it seems ridiculous to me! I am sure loss of habitat due to bad farming methods has much more to do with it and of course pesticides.

I enjoyed your Norfolk post, nice to see the Bullfinch. That of course is a species which suffered due to interference from man.

Lovely to see the Snowdrops on an earlier post too.

oldcrow61 said...

Why don't humans leave nature to take care of itself. I have to agree with what you say Pete.